Three-Degree-of-Freedom Homodyne Wavefront Interferometry Using Fiber Array

Homodyne wavefront interferometry enables synchronous compensation of angle error in precision displacement measurement. However, traditional decoupling method relies on image signal, the measurement speed is typically only some μm/s. This paper proposes a method that employs a fiber array for spatial sparse sampling, in order to achieve fast and simultaneous measurement of displacement, pitch, and yaw angle. A novel decoupling algorithm is developed to calculate the three degree of freedom, based on elliptic trajectory formed by a few sampling point inside an interference beam spot. Experiment results indicated that the prototype can achieve a measurement speed of 158.2mm/s, while the resolution can achieve 0.6 nm and 0.13 μ rad. The prototype was compared against commercial interferometer and autocollimator, the difference was at nanometer and micro-rad level. Further, the prototype was used to calibrate a commercial piezo stage. The maximum motion speed of the stage is 3.3mm/s，within a motion range of 100 μm, the repeatability achieves 1nm and the linear error is below 10nm.